1. Field of the Invention
The invention relates to a child-resistant, or safety closure, comprising two nested closure members, which must be manipulated in a particular complex manner in order to remove the closure from an associated container.
2. Description of the Prior Art
Child-resistant closures comprising two nested closure members are well known in the art. Typically, the inner and outer members of these closures are provided with cooperating sets of lugs which engage each other when the outer member is rotated in the direction to apply the closure to an associated container. When the outer member is rotated in the removal direction, these lugs cam or ratchet past each other on inclined surfaces, so that the closure cannot be removed by mere rotation. To provide positive engagement of the inner and outer closure members for removal, the prior art has employed additional separate sets of cooperating lugs or projections, which are normally held completely separated by a resilient means. To remove these closures, the outer member must be variously squeezed, pushed, or otherwise manipulated to overcome the resilient separating means, and bring the respective removing lugs of the set into positive driving engagement.
The prior art devices thus employ different sets of cooperating lugs to apply and remove the safety closure. In many prior art devices if the separating means is damaged such as by abuse, storage with a top load or simply by repeated use, the outer closure member can fall into positive engagement with the inner member, thereby defeating the safety feature. A typical example of prior art devices of this general type is disclosed by U.S. Pat. No. 3,776,407 to Cistone. Cistone discloses two nested closure members having cooperating ratcheting lugs on each of the respective member skirt walls, and positively engaging lugs on the respective member panels. Resilient segments on at least one panel normally separate the positively engaging panel lugs.
Where continued use of a safety closure is not anticipated, as for containers of products which will be used upon one opening, low closure cost is relatively more important than fidelity of repetitive operation. Accordingly, in some applications, resilient separating means are not employed. Rather, the user must hold the outer member of the closure downwardly against the camming force to provide a frictional engagement of lugs which would otherwise cam past each other. Exemplifying such closures as U.S. Pat. No. 3,946,890 to Scuderi, U.S. Pat. No. 4,241,840 to Willis, and British Pat. No. 1,529,999 to Zeller Plastik.
In other prior art devices, at least one of the closure member panels is contoured to function as the resilient means separating sets of lugs. Such resilient panels are disclosed in U.S. Pat. Nos. 3,472,411 to Turner and 3,853,236 to Ostrowsky.